Prediction of the future development trend of C++ inline functions

Inline functions in C will continue to evolve with the development of standards: 1. The constexpr function allows the use of inline functions in constant expressions to improve performance; 2. Template inline functions provide versatility and avoid creating multiple Function; 3. Inline functions in different compilation units allow inline functions to be included in public header files to achieve privatization of details. Practical cases prove that inline functions can significantly improve code performance.

Prediction of the future development trend of C inline functions

Inline functions are a compiler optimization technology that allows functions The code is embedded directly into the function that calls it, thus avoiding the overhead of function calls. In C, inline functions can be declared by using the inline keyword.

The advantages of inline functions include:

• Reduce the overhead of function calls
• Improve code readability

However, inline Linked functions also have certain disadvantages:

• May increase code size
• May lead to extended compilation time

With the continuous development of the C standard, The future development trend of inline functions is expected to be as follows:

1. constexpr function

C 11 introduced the constexpr keyword, allowing compile-time The evaluated expression is marked. This allows inline functions to be used with constant expressions, further improving performance.

2. Template inline functions

C 17 allows inline functions to be used in templates. This enables developers to create more general inline functions and avoid the need to create multiple functions when working with different types.

3. Inline functions in different compilation units

In C 20, inline functions will be allowed to be declared in different compilation units. This allows developers to include inline functions in public header files and use them as private implementation details.

Practical case

The following is a practical case showing how inline functions can improve code performance:

#include <iostream>

// 非内联函数
int add_noninline(int x, int y) {
  return x + y;
}

// 内联函数
inline int add_inline(int x, int y) {
  return x + y;
}

int main() {
  int sum_noninline = 0;
  int sum_inline = 0;

  // 使用非内联函数进行 10000 次求和操作
  for (int i = 0; i < 10000; i++) {
    sum_noninline += add_noninline(i, i);
  }

  // 使用内联函数进行 10000 次求和操作
  for (int i = 0; i < 10000; i++) {
    sum_inline += add_inline(i, i);
  }

  std::cout << "非内联函数求和结果：" << sum_noninline << std::endl;
  std::cout << "内联函数求和结果：" << sum_inline << std::endl;

  return 0;
}

Run this code, you can see the internal Inline functions add_inline execute much faster than non-inline functions add_noninline.

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